diff --git a/ChangeLog b/ChangeLog
index 02832f48ae..d51ea17082 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+Fri Feb 15 00:15:31 2013  Tanaka Akira  <akr@fsij.org>
+
+	* ext/socket/sockport.h (VALIDATE_SOCKLEN): new macro to validate
+	  sa_len member of 4.4BSD socket address.
+
+	* ext/socket/getnameinfo.c (getnameinfo): use VALIDATE_SOCKLEN,
+	  instead of SA_LEN.
+
+	* ext/socket/socket.c (sock_s_getnameinfo): use VALIDATE_SOCKLEN
+	  instead of SS_LEN. 
+
 Thu Feb 14 22:25:54 2013  Tanaka Akira  <akr@fsij.org>
 
 	* ext/socket/socket.c (sockaddr_len): extracted from sockaddr_obj.
diff --git a/ext/socket/getnameinfo.c b/ext/socket/getnameinfo.c
index d1d5ff6c73..d0c17e1826 100644
--- a/ext/socket/getnameinfo.c
+++ b/ext/socket/getnameinfo.c
@@ -151,8 +151,8 @@ getnameinfo(const struct sockaddr *sa, socklen_t salen, char *host, socklen_t ho
 	if (sa == NULL)
 		return ENI_NOSOCKET;
 
-	len = SA_LEN(sa);
-	if (len != salen) return ENI_SALEN;
+	if (!VALIDATE_SOCKLEN(sa, salen)) return ENI_SALEN;
+        len = salen;
 
 	family = sa->sa_family;
 	for (i = 0; afdl[i].a_af; i++)
diff --git a/ext/socket/socket.c b/ext/socket/socket.c
index bae6bf288c..be3f8cc4f1 100644
--- a/ext/socket/socket.c
+++ b/ext/socket/socket.c
@@ -1235,7 +1235,7 @@ sock_s_getnameinfo(int argc, VALUE *argv)
 	    rb_raise(rb_eTypeError, "sockaddr length too big");
 	}
 	memcpy(&ss, RSTRING_PTR(sa), RSTRING_LEN(sa));
-	if ((size_t)RSTRING_LEN(sa) != SS_LEN(&ss)) {
+        if (!VALIDATE_SOCKLEN((struct sockaddr *)&ss, RSTRING_LEN(sa))) {
 	    rb_raise(rb_eTypeError, "sockaddr size differs - should not happen");
 	}
 	sap = (struct sockaddr*)&ss;
diff --git a/ext/socket/sockport.h b/ext/socket/sockport.h
index 5ab087d97b..43784fca61 100644
--- a/ext/socket/sockport.h
+++ b/ext/socket/sockport.h
@@ -10,6 +10,12 @@
 #ifndef SOCKPORT_H
 #define SOCKPORT_H
 
+#ifdef HAVE_STRUCT_SOCKADDR_SA_LEN
+# define VALIDATE_SOCKLEN(addr, len) ((addr)->sa_len == (len))
+#else
+# define VALIDATE_SOCKLEN(addr, len) ((void)(addr), (void)(len), 1)
+#endif
+
 #ifdef SA_LEN
 #  define SS_LEN(ss) (ss)->ss_len
 #else